The present invention relates to improvements in blowing sand molding machines.
The improvements here described are included in that type of machine which includes a frame to the upper part of which is supported a hopper wherein molding sand is stored.
The hopper is, at a given moment, in vertical alignment with a blowing cartridge which receives a portion of the said which, immediately and by means of a current of air under pressure blown into the interior of the cartridge, passes to corresponding master or pattern plates fixed to corresponding supports.
One object of the present invention is to provide an improved assembly of and structure for the supports for the master plates.
Another object of the invention is to provide an improved structure for and functioning of a gassing plate included in the molding sand blower.
A further object of the invention is to provide an improved device which permits air under pressure to enter the interior of the blowing cartridge.
The first object is achieved by longitudinally disposing on the frame of the machine and in a plane immediately below the blowing cartridge, a pair of cylindrical bars which act as guides for the supports of the master plates. These bars or guides extend along the front and rear zones of the frame of the machine, the bar of the front zone occupying a plane which is substantially lower than that occupied by the bar of the rear zone. With this arrangement, the front bar does not constitute an obstacle for the operator of the machine.
The supports of the master plates slide along the bars or guides through two different means: one consisting in manually driving one of the supports by means of controlling a wheel, and the other consisting in automatically driving the other support by means of a pressure cylinder.
The automatically driven support is formed of two halves. The rear half is guided on the cylindrical bars and the front half is hinged to the rear half and joined to the stem of another pressure cylinder which causes the front half to pivot in order to deposit a produced mould on a conveyor belt.
The second object of the invention is achieved by placing the gassing plate on arms which hang from rails located at opposite sides of the blowing cartridge. These arms incorporate wheels which slide along the rails driven by a pressure cylinder. Under these conditions, the gassing plate is capable of alternatively moving within a horizontal plane to be located in the vertical plane of the master plates or to be withdrawn therefrom when the gassing of the sand stored in the plates has taken place.
The third object of the invention involves preventing drawbacks present in conventional sand blowers with respect to the couplings between the pressurized air duct and the blowing cartridge. In these conventional machines, such coupling is a complicated assembly of ducts wherein the air looses pressure and, consequently, its action on the sand is weakened.
With the device of the invention, the tightness necessary between the pressurized air duct and the blowing cartridge is maintained constant, in spite of movements to be made by the cartridge.
In general terms, such device of the invention includes a nozzle which is tightly coupled to an inlet formed sideways in the blowing cartridge which receives the sand from the feed hopper. In one position of the blowing cartridge, the nozzle is in alignment with a block member to which a flexible pipe, through which the pressurized air passes to the interior of the cartridge, is connected. The block member is mounted on a vertically disposed guide along which it is capable of being moved downwardly by the blowing cartridge when the same descends to be tightly coupled to a core box formed by the plates. The block member is returned to its original position by a spring when the nozzle leaves the block member at a time at which the blowing cartridge is again directed to the hopper to collect a new load of sand.